[Elecraft] KAT500 Attenuator

[Lyn Norstad]

Andy -

My KAT500 (s/n 2916) behaves pretty much the same way.  I don't know if R7
is present, but tuning into my normal antenna produces these results:

Man/Auto (doesn't matter): Att Out = SWR 1.00
     "    "           "           "         Att IN = SWR 99.99

My guess is that the KAT500 cannot get a strong enough signal to tune
properly with the Attenuator IN.  Interestingly, when it was new, it did not
have that problem.  Perhaps R7 has failed.

73
Lyn, W0LEN

PS - Where did you find KAT500 rev C schematics?
Thx.




-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Andy Durbin
Sent: Friday, December 10, 2021 7:30 AM
To: elecraft at mailman.qth.net
Subject: [Elecraft] KAT500 Attenuator

KAT500 has an input attenuator that may, under certain conditions, be
activated during a full search tune.   Page 1 rev C of the KAT500 schematic
shows the attenuator is a divider consisting of R6 and R7 which are both 39
ohm.  My KAT500 serial number 2609 does not have R7 fitted and R7 is shown
as not populated in Figure 17 of KAT500 User's Manual Rev C6.

The removal of R7 changes the potential divider into a simple series
resistor and my measurements show my KAT500 presents a very poor match to my
TS-590 exciter when the attenuator is active.  In this example the KAT500
was in bypass and connected to a nominal 50 ohm dummy load.  The impedance
presented to my TS-590 by KAT500 was measured with an LP-100A:

Att Out:  R 48.1, X 2.4, Pwr 4.48, SWR 1.06
Att In:      R 22.3, X 162.6, Pwr 0.55,  SWR 9.98

Do other KAT500 owners see similar results? (Attenuator can be switched
in/out with KAT500 utility)

Can someone please explain why the attenuator was changed.

Thanks and 73,
Andy k3wyc




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